Specifications for metal castings, forgings and premium mill products such as plate, bar and extrusion, frequently include tensile elongation minima among their lot acceptance requirements. Elongations are measured using tensile test specimens, e.g., “coupons,” made from specially cast bars (“prolongs”), or material that is excised from the manufactured parts themselves, which are stretched in specialized tensile testing machines. In addition to the cost of the materials consumed in these tests, there are also significant costs associated with the machining and testing of the specimens. Furthermore, the specimens may not adequately represent the true bulk material properties of the parts being evaluated, which can lead to erroneous test results.
A long-felt but as yet unsatisfied need therefore exists in the manufacturing industry for reliable, low-cost, apparatus and methods for the nondestructive verification of the minimum tensile elongation specification of a manufactured part that can be effected on the part itself, thereby eliminating the need for expensive tensile test coupons and equipment, and any question whether such coupons accurately represent the true bulk material properties of the manufactured part.